RESUMO
In order to establish the nature and the distribution of mutations causing cystic fibrosis (CF) in 220 unrelated Argentine families, the present authors conducted an extensive molecular analysis of the CF transmembrane regulator (CFTR) gene. First, a direct mutation analysis of 13 common mutations was done, enabling the detection of 319 out of 440 CF alleles (72.52%). Then an exhaustive screening of the entire coding region and the adjacent sequences of the CFTR gene was performed in all patients carrying at least one unidentified CF allele using the multiplex heteroduplex analysis assay followed by direct DNA sequencing. Thirty-nine different CF mutations, including five previously undescribed mutations (i.e. L6V, Y362X, 1353insT, 2594delGT and 2686insT) and two novel polymorphisms (i.e. 1170G/C and 3315A/C) were identified. As a result, the overall detection rate increased by up to 83.45%. Besides DeltaF508, only five mutations showed frequencies higher than 1%. In addition, a total of 49% of the mutations were rare because they were found in only one CF family. This wide spectrum of CF mutations is in agreement with the heterogeneous ethnic origin of the Argentine population. The data obtained here may have important consequences for the development of adequate strategies for the molecular diagnosis of CF in Argentina.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/genética , Fibrose Cística/genética , Testes Genéticos , Argentina , Fibrose Cística/diagnóstico , Frequência do Gene , Heterogeneidade Genética , Humanos , Mutação , Polimorfismo GenéticoRESUMO
We conducted clinical and genetic analyses of 52 cystic fibrosis (CF) patients in Uruguay, which is about half of the known affected individuals in the country. A relatively high proportion had a mild presentation, characterized by pancreatic sufficiency (28), a strong pulmonary component (97), and borderline sweat electrolyte measurements (25). Mutational analysis of CF chromosomes demonstrated a relatively low incidence of the DeltaF508 allele (40) and a large number of other cystic fibrosis conductance regulator mutations, with an overall detection rate of about 71. Fifteen different mutations were detected in our patients: DeltaF508, G542X, R1162X, G85E, N1303K, R334W, R75Q, R74W, D1270N, W1282X, DeltaI507, 2789+5G-->A, R1066C, -816C/T, R553X, as well as RNA splicing variant IVS8-5T. This group of Uruguayan CF patients has some characteristics in common with other populations of similar origin (Hispanics), as well as some unique characteristics
Assuntos
Humanos , Fibrose Cística/genética , Mutação/genética , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Alelos , Análise Mutacional de DNA , Genótipo , UruguaiRESUMO
We have analyzed 97 CF unrelated Mexican families for mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Our initial screening for 12 selected CFTR mutations led to mutation detection in 56.66% of the tested chromosomes. In patients with at least one unknown mutation after preliminary screening, an extensive analysis of the CFTR gene by single stranded conformation polymorphism (SSCP) or by multiplex heteroduplex (mHET) analysis was performed. A total of 34 different mutations representing 74.58% of the CF chromosomes were identified, including five novel CFTR mutations: W1098C, P750L, 846delT, 4160insGGGG and 297-1G-->A. The level of detection of the CF mutations in Mexico is still lower than that observed in other populations with a relatively low frequency of the deltaF508 mutation, mainly from southern Europe. The CFTR gene analysis described here clearly demonstrated the high heterogeneity of our CF population, which could be explained by the complex ethnic composition of the Mexican population, in particular by the strong impact of the genetic pool from southern European countries.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/genética , Fibrose Cística/genética , Fibrose Cística/epidemiologia , Feminino , Frequência do Gene , Variação Genética , Humanos , Masculino , México/epidemiologia , Mutação , Polimorfismo Conformacional de Fita SimplesRESUMO
The diagnosis of cystic fibrosis (CF) is not always certain, despite extensive clinical evaluation, multiple sweat chloride tests, and genotype analysis. We hypothesized that nasal transepithelial potential difference measurements have a useful role in this situation. In 11 patients without an established diagnosis of CF, results of simultaneous nasal potential difference (PD) and sweat chloride measurements were compared with those from control subjects, obligate CF heterozygotes, and patients with a confirmed diagnosis of CF. Two patients conformed to the PD profile for CF patients, whereas nine had values corresponding to those of the healthy control subjects. Subsequently the 5-thymidine (IVS8-5T) CF gene variant was identified in the two patients with abnormal PD measurements.
Assuntos
Fibrose Cística/diagnóstico , Mucosa Nasal/fisiopatologia , Adolescente , Adulto , Estudos de Casos e Controles , Criança , Fibrose Cística/genética , Fibrose Cística/fisiopatologia , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Insuficiência Pancreática Exócrina/diagnóstico , Feminino , Heterozigoto , Humanos , Masculino , Potenciais da Membrana/fisiologia , Mutação , Fenótipo , Suor/químicaRESUMO
OBJECTIVE: To compare differences in epithelial chloride conductance according to class of mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. METHODS: We evaluated the relationship between the functional classes of CFTR mutations and chloride conductance using the first diagnostic sweat chloride concentration in a large cystic fibrosis (CF) population. RESULTS: There was no difference in sweat chloride value value between classes of CFTR mutations that produce no protein (class I), fail to reach the apical membrane because of defective processing (class II), or produce protein that fails to respond to cyclic adenosine monophosphate (class III). Those mutations that produce a cyclic adenosine monophosphate-responsive channel with reduced conductance (class IV) were associated with a significantly lower, intermediate sweat chloride value. However, patients with the mutations that cause reduced synthesis or partially defective processing of normal CFTR (class V) had sweat chloride concentrations similar to those in classes I to III. CONCLUSION: Studies of differences in chloride conductance between functional classes of CFTR mutations provide insight into phenotypic expression of the disease.